Leak Detector: Description and Operation

Description

NVLD(Natural Vacuum Leakage Detection) module is located between the canister and the fuel tank air filter.
NVLD module is an integral part of the monitoring system. The NVLD module has a pressure switch and a temperature sensor. The temperature and pressure switch are checked every 10 minutes during engine off.
While the vehicle is turned off, the temperature and pressure switch monitored. As the fuel system cools down, the pressure should drop. The Evap system checks for small leaks by checking the pressure switch state as the temperature changes. If the pressure does not drop enough as the temperature drops, a leak is detected.
It closes off the air inlet to the canister for the Evaporative Emissions System and also prevents fuel vapors from escaping from the Canister when the vehicle is not operating.
When the switch is closed due to pressure decrease, a timer is started and switch closed duration is monitored
This information will be provided to the ECM for very small leak error detection.Large leak/ fuel cap off detection is performed during engine running.